Not all of the kit or ARF products have a recommendation for gas engines - most only provide 2- and 4-stroke glow engine recommendations. I'd like to start using some of the new small gas engines coming on the market, but how can they be related to a recommended glow engine size? For example, if a .60-sized plane has a .60 2-stroke or .90 4-stroke recommendation, what should the gas engine for this size plane be? Is there a rule of thumb, like using the 4-stroke size as a basis? If so, then the plane above could use a 15cc gas engine (.90 cu in is about 15 cc). I know some have a "bigger is better" attitude toward engine sizes, but I'd like to keep the weight down as much as possible yet still have a setup that performs well. Or does the performance of a 2-stroke gas engine offset its greater weight?
Thanks,
Bidwin

I would say...just google the airplanes you like and the engines you like....and start reading....more and faster results. Capt,n

yeah this is a minefield as I am discovering.

Some manufactures (ARF) specifiy their planes according to the minimum 2 stroke size engine to fly the things. So BH Models will tell you .60 size so that means .60 OS or something similar. If they have no 4 stroke recommendation then it means there is not sufficient space from the firewall to the prop hub to mount a 4 stroke without modifying something.

Others provide a 2 and 4 stroke recommendation.

When deciding to fit a gasoline engine I look at the 4 stroke recommendation and simply opt for the equivalent gasoline engine eg. if it says 1.20 4 stroke then a 20cc gasser is good to go.
This is mostly to fit the enine on thesupplied engine mount and maintain CG.

also worthwhile remebering that every 10cc = 0.6cubic inches or .60size glow engine.

Which engine you opt for is really a matter of reading. These new gassers seem to be a lot lighter and more powerful than their predecessors so their performance exceeds the 4 stroke equivalent and closes the gap to the 2 stroke glow engines.

First, I know there will be many opinions and different answers to your question. So, consider this JMHO.

Bigger is better. I don't think so. More power just changes the "performance". More power but heavier just makes "some" airframes faster while increasing the wingloading which makes the airframe fly in a less responsive manner. There has to be a balance somewhere and that usually lies in the eyes of the beholder.


Power Equivalents - all dle
DLE 20 = glow 1.20 while being heavier.
DLE 30 = glow 1.80 while being heavier.

I fly a couple of each of these and really enjoy them. But, I try to find an airframe with light wingloading as I enjoy flying that type of plane.

Scale flyers have different goals than a sport or 3D flyer.

so the DLE is the measure of things?

I think so. Based on power to weight as well as bucks spent for bang received. Not going to argue the fact there are better or more powerful available.

Nope, just what I have personal experience with. Add your experience.

Bidwin,

I replaced an OS 120 FS with a DLE 20. OS 120 w/muffler weights about 32 oz. DLE 20 weights 29 oz with muffler and ignition modual. But it will need a battery so weight comes out about the same. The DLE 20 is slightly longer front to back than the OS so you should measure for that or expect to modify the firewall area. You have more flexability re the cg because you can put the battery were needed for cg. On one of my gassers I had to put both batteries under the cowling to get cg. On another I put the battery way back in the tail under the rear stablizers to balance. The DLE turns the same prop 300 rpm more static that the 120. Also the DLE is shorter top to bottom except for the spark plug boot. I've put DLE 20s on airplanes from so called 60 size to 120 size. I'll admit the 60 size is somewhat over powered, but the 15-17 cc gasser have about half the power of the DLE 20 and are only an ounce or two lighter. I have a couple of RCGF 20cc gassers. They are heavier at about 38 oz. Ok if you need the weight. On flys a 90 size plane just fine. The other is on a 120 size plane and is "just enough". The DLE turns the same prop about 500 rpm more than the RCFG.

In our maturing economy, DLE is the standard. They are considered top tier of the ubiquitous ARF market. Guys like you with a lot of areo/mechanical knowledge, experience, and high standards are not too common anymore.

Thank you. Finally, the info I have been searching for.

I thought this cleared things up for me. Until I started thinking, always a dangerous proposition.

What 90 sized plane do you mean? and what 120 size? What are the wingspans?

A 1/4 scale cub recommends a 90-120 FS, 108" wingspan. So does a Goldberg Extra, 68" wingspan, same engine recommendation.
Are these 90, or 120 sized?

So I presume the Goldberg tips towards the 20cc DLE being a bit too much?

I flew an old Goldberg Extra 300 for some years with an RCGF 20cc engine, that while a decent running engine was no match for the DLE 20. The DLE 20 in an old GB Extra would be a great choice, based on my experience with that airframe.
Pete

Cloud 9, several months late but I'll try to answer your question. The RCGF is a rear carb 20cc in a 72" wing span KMP Hurricane, wtg 13.2 lbs. The power is just enough. Flies scale. The other RCGF 20cc is a side carb in a BH "90 size" they call it, P-40 converted to a P-36. 65.5" wingspan, wtg 11.5 lbs about. Flies better than scale but not grossly overpowered. The DLE 20 puts out noticeably more power than the RCGF.

Wanting to put a 20 Dale or valley view 20 on a hangar 9 Christian Eagle, I also have a evolution 26, or would the 26 be too much, the plane call for a 90 to 120

I would go with the 26.

Thank you!